From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EEE94C43331 for ; Tue, 31 Mar 2020 06:15:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A8BAB20757 for ; Tue, 31 Mar 2020 06:15:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="n1y0aOZj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726533AbgCaGPN (ORCPT ); Tue, 31 Mar 2020 02:15:13 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:37722 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726001AbgCaGPN (ORCPT ); Tue, 31 Mar 2020 02:15:13 -0400 Received: by mail-wr1-f67.google.com with SMTP id w10so24446317wrm.4 for ; Mon, 30 Mar 2020 23:15:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mRVnmzdHBnbaq4PfERFrCjdz7LFeII2yKgpOCl8UeMw=; b=n1y0aOZj60mURAb8JJLZ7OyRLYYG15KXRiKJWINW5MS/zQ4zAUns24u1jM+OI30j4G z0j9uWkP+2uVohcflcn2OYVFRShbKvhXSwszehedmagGbYDKeHezWtrUZeHPCu464mv3 mUHeSQwGI55p5l8bYfyUF54pukeqsxHqryc7BQ2/PYrizuNaVahSicPF2ANiSyIz80m1 Jew325ckLWGaICwR4YI3sKiYTxhHwaVrtkAyjoFbHQMQf9wY7DbeegjitrXyQjwlcZ6B gKzIuWesSDr06eaFjEXJ89yurzgSkM3KCxCn/cpX1Uz6mlV2FwMk/OPK14TqtE3F1hhN k4rg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mRVnmzdHBnbaq4PfERFrCjdz7LFeII2yKgpOCl8UeMw=; b=FeHfSc4OeF8dLrxIlZbn+wwsGZfFPlX1ZCSjDhXk7j0xJdCtuR5mn2PEOKByN27Byh Q5hQobVZqvh49shpz3KWno2EmMj3v9RQ2F0Wy0L+sl2GgGPmGHreadxuJey9ZYGBLO5e hu/g06UGcNp+a5SoaZkK9BOMUSr+Hxyznix25R+nbmNvuj96yQiziW6goJ/1C9PE0tv4 rjfXWReomIrTePC3pNDah24tVO2JhDM6CDw3EAtSiPZnD7BaKZjfSjaxPoY7AkxC9aGO UfrknLnEddfpCxMjy86vnQuafLLuLylVKK25OKqw80gC66mtdB2fcwI7HPCBXD7uCuX2 /xSA== X-Gm-Message-State: ANhLgQ14sNu1FWt8jV5f3k/GayolX/+CKrZWzrq4k89fz/kG2O0/aFuX JUmTBLCcO8D0k7uV2A2S4mfRBUO1pbR52dxQaYs9BA== X-Google-Smtp-Source: ADFU+vs0F92a6eE7vc2sCJMcPKbVh7lfFAZr1hwa1/UHth3pR6DQxKUueEXk9b2hWC++G4rgzzsn3XSqweCCJviO1zU= X-Received: by 2002:adf:9b96:: with SMTP id d22mr19832564wrc.249.1585635309395; Mon, 30 Mar 2020 23:15:09 -0700 (PDT) MIME-Version: 1.0 References: <20200226004608.8128-1-trishalfonso@google.com> <4b8c1696f658b4c6c393956734d580593b55c4c0.camel@sipsolutions.net> <674ad16d7de34db7b562a08b971bdde179158902.camel@sipsolutions.net> <2cee72779294550a3ad143146283745b5cccb5fc.camel@sipsolutions.net> In-Reply-To: From: David Gow Date: Mon, 30 Mar 2020 23:14:57 -0700 Message-ID: Subject: Re: [PATCH] UML: add support for KASAN under x86_64 To: Johannes Berg Cc: Dmitry Vyukov , Patricia Alfonso , Jeff Dike , Richard Weinberger , Anton Ivanov , Andrey Ryabinin , Brendan Higgins , linux-um , LKML , kasan-dev Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="00000000000064aa9705a2207df3" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --00000000000064aa9705a2207df3 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Mar 30, 2020 at 1:41 AM Johannes Berg w= rote: > > On Mon, 2020-03-30 at 10:38 +0200, Dmitry Vyukov wrote: > > On Mon, Mar 30, 2020 at 9:44 AM Johannes Berg wrote: > > > On Fri, 2020-03-20 at 16:18 +0100, Dmitry Vyukov wrote: > > > > > Wait ... Now you say 0x7fbfffc000, but that is almost fine? I thi= nk you > > > > > confused the values - because I see, on userspace, the following: > > > > > > > > Oh, sorry, I copy-pasted wrong number. I meant 0x7fff8000. > > > > > > Right, ok. > > > > > > > Then I would expect 0x1000 0000 0000 to work, but you say it doesn'= t... > > > > > > So it just occurred to me - as I was mentioning this whole thing to > > > Richard - that there's probably somewhere some check about whether so= me > > > space is userspace or not. > > > > > > I'm beginning to think that we shouldn't just map this outside of the > > > kernel memory system, but properly treat it as part of the memory tha= t's > > > inside. And also use KASAN_VMALLOC. > > > > > > We can probably still have it at 0x7fff8000, just need to make sure w= e > > > actually map it? I tried with vm_area_add_early() but it didn't reall= y > > > work once you have vmalloc() stuff... > > > > But we do mmap it, no? See kasan_init() -> kasan_map_memory() -> mmap. > > Of course. But I meant inside the UML PTE system. We end up *unmapping* > it when loading modules, because it overlaps vmalloc space, and then we > vfree() something again, and unmap it ... because of the overlap. > > And if it's *not* in the vmalloc area, then the kernel doesn't consider > it valid, and we seem to often just fault when trying to determine > whether it's valid kernel memory or not ... Though I'm not really sure I > understand the failure part of this case well yet. > > johannes > I spent a little time playing around with this, and was able to get mac80211 loading if I force-enabled CONFIG_KASAN_VMALLOC (alongside bumping up the shadow memory address). The test-bpf module was still failing, though =E2=80=94 which may or may no= t have been related to how bpf uses vmalloc(). Simply adding code to unpoison the region on vmalloc() doesn't seem to do anything, which lends credence to the idea that the memory is actually being unmapped or is not considered kernel memory. I do like the idea of trying to push the shadow memory allocation through UML's PTE code, but confess to not understanding it particularly well. I imagine it'd require pushing the KASAN initialisation back until after init_physmem, and having the shadow memory be backed by the physmem file? Unless there's a clever way of allocating the shadow memory early, and then hooking it into the page tables/etc when those are initialised (akin to how on x86 there's a separate early shadow memory stage while things are still being set up, maybe?) Food for thought, perhaps. -- David --00000000000064aa9705a2207df3 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIPCgYJKoZIhvcNAQcCoIIO+zCCDvcCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg ggxtMIIEkjCCA3qgAwIBAgINAewckktV4F6Q7sAtGDANBgkqhkiG9w0BAQsFADBMMSAwHgYDVQQL ExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UEAxMK R2xvYmFsU2lnbjAeFw0xODA2MjAwMDAwMDBaFw0yODA2MjAwMDAwMDBaMEsxCzAJBgNVBAYTAkJF MRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMSEwHwYDVQQDExhHbG9iYWxTaWduIFNNSU1FIENB IDIwMTgwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCUeobu8FdB5oJg6Fz6SFf8YsPI dNcq4rBSiSDAwqMNYbeTpRrINMBdWuPqVWaBX7WHYMsKQwCOvAF1b7rkD+ROo+CCTJo76EAY25Pp jt7TYP/PxoLesLQ+Ld088+BeyZg9pQaf0VK4tn23fOCWbFWoM8hdnF86Mqn6xB6nLsxJcz4CUGJG qAhC3iedFiCfZfsIp2RNyiUhzPAqalkrtD0bZQvCgi5aSNJseNyCysS1yA58OuxEyn2e9itZJE+O 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<20200226004608.8128-1-trishalfonso@google.com> <4b8c1696f658b4c6c393956734d580593b55c4c0.camel@sipsolutions.net> <674ad16d7de34db7b562a08b971bdde179158902.camel@sipsolutions.net> <2cee72779294550a3ad143146283745b5cccb5fc.camel@sipsolutions.net> In-Reply-To: From: David Gow Date: Mon, 30 Mar 2020 23:14:57 -0700 Message-ID: Subject: Re: [PATCH] UML: add support for KASAN under x86_64 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============2264957797074666789==" Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: Johannes Berg Cc: Patricia Alfonso , Richard Weinberger , Jeff Dike , Brendan Higgins , LKML , kasan-dev , linux-um , Andrey Ryabinin , Dmitry Vyukov , Anton Ivanov --===============2264957797074666789== Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="000000000000649ae305a2207dcc" --000000000000649ae305a2207dcc Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Mar 30, 2020 at 1:41 AM Johannes Berg w= rote: > > On Mon, 2020-03-30 at 10:38 +0200, Dmitry Vyukov wrote: > > On Mon, Mar 30, 2020 at 9:44 AM Johannes Berg wrote: > > > On Fri, 2020-03-20 at 16:18 +0100, Dmitry Vyukov wrote: > > > > > Wait ... Now you say 0x7fbfffc000, but that is almost fine? I thi= nk you > > > > > confused the values - because I see, on userspace, the following: > > > > > > > > Oh, sorry, I copy-pasted wrong number. I meant 0x7fff8000. > > > > > > Right, ok. > > > > > > > Then I would expect 0x1000 0000 0000 to work, but you say it doesn'= t... > > > > > > So it just occurred to me - as I was mentioning this whole thing to > > > Richard - that there's probably somewhere some check about whether so= me > > > space is userspace or not. > > > > > > I'm beginning to think that we shouldn't just map this outside of the > > > kernel memory system, but properly treat it as part of the memory tha= t's > > > inside. And also use KASAN_VMALLOC. > > > > > > We can probably still have it at 0x7fff8000, just need to make sure w= e > > > actually map it? I tried with vm_area_add_early() but it didn't reall= y > > > work once you have vmalloc() stuff... > > > > But we do mmap it, no? See kasan_init() -> kasan_map_memory() -> mmap. > > Of course. But I meant inside the UML PTE system. We end up *unmapping* > it when loading modules, because it overlaps vmalloc space, and then we > vfree() something again, and unmap it ... because of the overlap. > > And if it's *not* in the vmalloc area, then the kernel doesn't consider > it valid, and we seem to often just fault when trying to determine > whether it's valid kernel memory or not ... Though I'm not really sure I > understand the failure part of this case well yet. > > johannes > I spent a little time playing around with this, and was able to get mac80211 loading if I force-enabled CONFIG_KASAN_VMALLOC (alongside bumping up the shadow memory address). The test-bpf module was still failing, though =E2=80=94 which may or may no= t have been related to how bpf uses vmalloc(). Simply adding code to unpoison the region on vmalloc() doesn't seem to do anything, which lends credence to the idea that the memory is actually being unmapped or is not considered kernel memory. I do like the idea of trying to push the shadow memory allocation through UML's PTE code, but confess to not understanding it particularly well. I imagine it'd require pushing the KASAN initialisation back until after init_physmem, and having the shadow memory be backed by the physmem file? Unless there's a clever way of allocating the shadow memory early, and then hooking it into the page tables/etc when those are initialised (akin to how on x86 there's a separate early shadow memory stage while things are still being set up, maybe?) Food for thought, perhaps. -- David --000000000000649ae305a2207dcc Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIPCgYJKoZIhvcNAQcCoIIO+zCCDvcCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg ggxtMIIEkjCCA3qgAwIBAgINAewckktV4F6Q7sAtGDANBgkqhkiG9w0BAQsFADBMMSAwHgYDVQQL ExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UEAxMK R2xvYmFsU2lnbjAeFw0xODA2MjAwMDAwMDBaFw0yODA2MjAwMDAwMDBaMEsxCzAJBgNVBAYTAkJF MRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMSEwHwYDVQQDExhHbG9iYWxTaWduIFNNSU1FIENB IDIwMTgwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCUeobu8FdB5oJg6Fz6SFf8YsPI dNcq4rBSiSDAwqMNYbeTpRrINMBdWuPqVWaBX7WHYMsKQwCOvAF1b7rkD+ROo+CCTJo76EAY25Pp jt7TYP/PxoLesLQ+Ld088+BeyZg9pQaf0VK4tn23fOCWbFWoM8hdnF86Mqn6xB6nLsxJcz4CUGJG qAhC3iedFiCfZfsIp2RNyiUhzPAqalkrtD0bZQvCgi5aSNJseNyCysS1yA58OuxEyn2e9itZJE+O 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